How did the united states acquire native american lands with such ease in the nineteenth century?

During the 19th century the U. S. Acquired native lands because of presidential efforts to purchase land like the Louisiana Purchase made by Thomas Jefferson. They also used military force to move Natives. The Trail of Tears, created by President Andrew Jackson, moved the Natives (like the Cherokee) to reservations in Oklahoma. Efforts to civilized people and take land for farming were large at the time.

It would be answer choice b (1975)